Non-aqueous electrolyte secondary battery

ABSTRACT

A negative electrode is characterized by its composite particles constructed in such a manner that at least part of the surrounding surface of nuclear particles containing at least one of tin, silicon and zinc as a constituent element, is coated with a solid solution or an inter-metallic compound, which is composed of, the element included in the nuclear particles, and at least one other element except the elements included in the nuclear particles selected from a group comprising group  2  elements, transition elements, group  12  elements, group  13  elements and group  14  elements except carbon of the Periodic Table. The present invention is characterized that the lithium content of the nuclear particles of the composite particles is 40-95 atomic percent of the theoretical limit of lithium content of each constituent element of the nuclear particles. Further, the batteries are first charged at a constant current and upon reaching the predetermined voltage, are charged at a constant voltage. The current density during charging are set at not more than 5 mA/cm 2  as a in the area where the positive and negative electrodes face each other.

This application is a U.S. National Phase application of PCTInternational application PCT/JP99/06688.

FIELD OF THE INVENTION

The present invention relates to non-aqueous electrolyte secondarybatteries and charging methods of the same, and especially relates tonon-aqueous electrolyte secondary batteries (hereinafter, batteries)with high energy density, whose electrochemical properties such ascharge/discharge capacity and charge/discharge cycle life have beenenhanced by improvements of negative electrode materials and non-aqueouselectrolytes.

BACKGROUND OF THE INVENTION

In recent years, lithium secondary batteries with non-aqueouselectrolytes, which are used in such fields as mobile communicationsdevices including portable information terminals and portable electronicdevices, main power sources of portable electronic devices, small sizedomestic electricity storing devices, motor cycles using an electricmotor as a driving source, electric cars and hybrid electric cars, havecharacteristics of a high electromotive force and a high energy density.

The lithium ion secondary batteries with an organic electrolyticsolution, which use carbon materials as negative electrode activematerials and lithium-containing composite oxides as positive electrodeactive materials, have higher voltage and energy density, and superiorlow-temperature properties compared with secondary batteries usingaqueous solutions. As these lithium ion batteries do not use lithiummetal in the negative electrode, they are superior in terms of cyclestability and safety, thus are now being commercialized rapidly. Lithiumpolymer batteries using macromolecular (polymer) gel electrolytes whichcontain an organic electrolytic solution, have been also underdevelopment as a new thin and light batteries.

When lithium metal with a high capacity is used as a negative electrodematerial, dendritic deposits are formed on the negative electrode duringcharging. Over repeated charging and discharging, these dendriticdeposits penetrate through separators and polymer gel electrolytes tothe positive electrode side, causing an internal short circuit. Thedeposited dendrites have a large specific surface area, therefore theirreaction activity is high. Thus, it reacts with plasticizers (solvents)of the polymer gel electrolytes, lowering charge/discharge efficiency.This raises the internal resistance of the batteries, causing someparticles to be excluded from the network of the electronic conduction,thereby lowering the charge/discharge efficiency of the battery. Due tothese reasons, the lithium secondary batteries using lithium metal as anegative electrode material have a low reliability and a short cyclelife.

Nowadays, lithium secondary batteries, which use, as a negativeelectrode material, carbon materials capable of intercalating andde-intercalating lithium ions, are commercially available. In general,lithium metal does not deposit on negative electrodes with carbon. Thus,short circuits are not caused by dendrites. However, the theoreticalcapacity of graphite which is one of the currently used carbon materialsis 372 mAh/g, only one tenth of that of pure Li metal.

Other known negative electrode materials include pure metallic materialsand pure non-metallic materials which form compounds with lithium. Forexample, composition formulae of compounds of tin (Sn), silicon (Si) andzinc (Zn) with the maximum theoretical amount of lithium arerespectively Li₂₂Sn₅, Li₂₂Si₅, and LiZn, and within the range of thesecomposition formulae, metallic lithium does not normally deposit. Thus,an internal short circuit is not caused by dendrites. Furthermore,electrochemical capacities between these compounds and each element inits pure form mentioned above is respectively 993 mAh/g, 4199 mAh/g and410 mAh/g; all are larger than the theoretical capacity of graphite.

As other compound negative electrode materials, the Japanese PatentLaid-open Publication No. H07-240201 discloses a non-metallic silicidecomprising transition elements. The Japanese Patent Laid-openPublication No. H09-63651 discloses negative electrode materials whichare made of inter-metallic compounds comprising at least one of group 4Belements, phosphorus (P) and antimony (Sb), and have a crystal structureof one of the CaF2 type, the ZnS type and the AlLiSi type.

However, the foregoing high-capacity negative electrode materials havethe following problems.

Pure metallic and pure non-metallic materials used as negative electrodematerials, and which form compounds with lithium, commonly have inferiorcharge/discharge cycle properties compared with carbon negativeelectrode materials. The reason for this is assumed to be destruction ofthe negative electrode materials caused by volume expansion andcontraction.

On the other hand, as negative electrode materials with improved cyclelife properties, unlike the foregoing pure materials, the JapanesePatent Laid-open Publication No. H07-240201 and the Japanese PatentLaid-open Publication No. H09-63651 respectively disclose non-metallicsilicides composed of transition elements and inter-metallic compoundscomposed of at least one of group 4B elements, phosphorus (P) andantimony (Sb), and with a crystal structure of one of the CaF2 type, theZnS type and the AlLiSi type.

Batteries with negative electrode materials comprising non-metallicsilicides composed of transition elements, and disclosed in the JapanesePatent Laid-open Publication No. H07-240201, have improvedcharge/discharge cycle properties compared with lithium metal negativeelectrode material, in terms of the capacities of embodiments of theinvention and a comparative example at the first cycle, the fiftiethcycle and the hundredth cycle. However, when compared with a naturalgraphite negative electrode material, the increase in the capacity ofthe battery is only about 12%.

The materials disclosed in the Japanese Patent Laid-open Publication No.H09-63651 have a better charge/discharge cycle property than a Li-Pballoy negative electrode material according to an embodiment and acomparative example. The materials also have a larger capacity comparedwith a graphite negative electrode material. However, the dischargecapacity decreases significantly until the 10-20th charge/dischargecycles. Even when Mg₂Sn, which is considered to be better than any ofthe other materials, is used, the discharge capacity decreases toapproximately 70% of the initial capacity after about the 20th cycle.Thus, they are inferior in terms of charge/discharge properties.

Regarding charging methods for these batteries, the Japanese PatentLaid-open Publication No. H06-98473 discloses a method in which a pulsecurrent is added while charging a lithium secondary battery in order torestrict dendritic deposits of lithium on a lithium negative electrode.As for lithium ion secondary batteries whose negative electrodescomprise carbon materials, the Japanese Patent Laid-open Publication No.H04-206479 discloses a method in which the level of a charging currentis controlled so as to be under a predetermined level during charging ata constant voltage in order to prevent lithium dendrites from depositingon a carbon negative electrode.

However, the charge/discharge cycle life properties vary depending onthe charging method for the batteries. The predominant reason for thisis as follows; since oxidation reduction potential during charging andvalues of over-voltage during electrochemical reaction are different, ifcharging current or voltage exceed predetermined tolerances, electrodereactions proceed unevenly, or other side reactions such as deposits oflithium, formation of film or generation of gas occur, thus lowering thecharge/discharge cycle life properties.

The present invention aims to address the foregoing problems of theconventional batteries.

SUMMARY OF THE INVENTION

The negative electrode of the batteries of the present invention ischaracterized by its main material which uses composite particlesconstructed in such a manner that at least part of the surroundingsurface of nuclear particles containing at least one of tin, silicon andzinc as a constituent element, is coated with a solid solution or aninter-metallic compound which is composed of,

the element included in the nuclear particles and

at least one other element (exclusive of the elements included in thenuclear particles) selected from a group comprising group 2 elements,transition elements, group 12 elements, group 13 elements and group 14elements (exclusive of carbon) of the Periodic Table.

The present invention is further characterized by one of the followingconditions:

the lithium content of the nuclear particles of the composite particlesis 40-95 atomic percent of the theoretical limit of lithium content ofeach constituent element of the nuclear particles, namely, tin, siliconand zinc;

the lithium content in the composite particles is 50-90 atomic percentof their theoretical limit of lithium content; and

when the negative electrode, exclusive of the current collector,contains an amount of lithium which allows no lithium to beelectro-deposited, the volume expansion of the negative electrodeexclusive of the current collector is 110-200%.

Further, according to the present invention, the batteries whosenegative electrode comprises the composite particles, are charged at apredetermined constant current (I) until they reach a predeterminedvoltage (E), and upon reaching the predetermined voltage (E), charged atthe predetermined constant voltage (E). The values of the current (I)and the current during the constant voltage charging are set at not morethan 5 mA/cm² as a current density in the area where the positive andnegative electrodes face each other.

With the foregoing construction, the problems associated with theconventional batteries are solved, thus providing non-aqueouselectrolyte secondary batteries and their charging methods achievinghigh-energy density and superior cycle life properties.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

FIG. 1 shows a vertical cross section of a cylindrical non-aqueouselectrolyte battery of the present invention.

FIG. 2 is a graph schematically showing charging current and voltageaccording to the charging method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The batteries of the present invention comprise positive and negativeelectrodes capable of intercalating and de-intercalating of lithium,non-aqueous electrolyte and separators or solid electrolytes.

As a negative electrode material used in the present invention,composite particles whose nuclear particles composed of solid phase Aare coated with solid phase B over the entire surface or part of thesurface, are used. The solid phase A contains at least one of tin,silicon and zinc as a constituent element. The solid phase B is composedof a solid solution or an inter-metallic compound which are composed of

at least one of tin, silicon and zinc, and

at least one other element (exclusive of the foregoing constituentelements) selected from a group comprising group 2 elements, transitionelements, group 12 elements, group 13 elements and group 14 elements(exclusive of carbon) of the Periodic Table. Hereinafter, the foregoingnegative electrode materials are called composite particles. When thecomposite particles are used as a negative electrode material, the solidphase B helps to suppress expansion and shrinkage of the solid phase Acaused by charging and discharging, thereby achieving a negativeelectrode material with superior charge/discharge cycle properties.

The present invention requires a content of lithium as follows:

the lithium content in the nuclear particles of the composite particlesbe 40-95 atomic percent of the theoretical limit of lithium content ofeach constituent element, namely, tin, silicon and zinc;

the lithium content in the composite particles be 50-90 atomic percentof their theoretical limit of lithium content; or

when the negative electrode exclusive of the current collector containsan amount of lithium which allows no electro-deposition of lithium tooccur, volume expansion of the negative electrode exclusive of thecurrent collector be 110-200%.

Further, according to the present invention, charging is carried outcombining two charging regions;

a constant current charging region wherein the batteries are charged ata constant current (I) until reaching a predetermined voltage (E); and

a constant voltage charging region, after reaching the predeterminedvoltage (E), wherein the batteries are charged at the predeterminedvoltage (E). The charging current in the constant current chargingregion and the constant voltage charging region are set at not more than5 mA/cm² as a current density of the area where the positive and thenegative electrodes face each other.

With the foregoing construction, the batteries of the present inventionenjoy a higher capacity and smaller reduction rates in the dischargecapacity up to the 10-20th charge/discharge cycles.

It is considered that the solid phase A of the negative electrodematerial of the present invention mainly contributes to a highercharge/discharge capacity since it contains at least one of Sn, Si andZn as a constituent element, and the solid phase B which coats part orentire surface of the nuclear particles comprising the solid phase A,contributes to improvement of the charge/discharge cycle properties. Theamount of lithium contained in the solid phase B is normally less thanthat contained in metal, a solid solution or an inter-metallic compound.

In other words, the negative electrode material used in the presentinvention is constructed such that particles which contain at least oneof high-capacity Sn, Si and Zn as a constituent element, are coated withthe solid solution or the inter-metallic compound, which are resistantto pulverization. The solid solution or the inter-metallic compound inthe coating layer prevents significant changes in crystal structure, inother words, significant changes in the volume of the nuclear particlescaused by electrochemical intercalating and de-intercalating of lithium.In this manner, pulverization of the nuclear particles is restricted.

The following is a manufacturing method of composite particles used forthe negative electrode materials.

In one manufacturing method of the composite materials, a fused mixtureof elements contained in the composite particles at a predeterminedcomposition ratio is quenched and solidified by dry-spraying,wet-spraying, roll-quenching or turning-electrode method. The solidifiedmaterial is treated with heat lower than the solid phase linetemperature of a solid solution or an inter-metallic compound. The solidphase line temperature is determined by the composition ratio. Theprocess of quenching and solidifying of the fused mixture allows thesolid phase A to deposit as a nucleus of a particle, and at the sametime, allows the solid phase B, which coats part of or the whole surfaceof the solid phase A, to deposit. The heat treatment following theforegoing process enhances evenness of the solid phase A and the solidphase B. Even when the heat treatment is not conducted, compositeparticles suitable for the present invention can be obtained. Apart fromthe quenching method mentioned above, other methods are applicableproviding they can quench the fused mixture rapidly and adequately.

In another manufacturing method, a layer of deposits comprisingessential elements in forming solid phase B is formed on the surface ofthe powder of the solid phase A. The layer is heat treated attemperatures lower than the solid phase line temperature. This heattreatment allows constituent elements within the solid phase A todisperse throughout the deposit layer to form the solid phase B as acoating layer. The deposit layer can be formed by plating or by amechanical alloying method. In the case of the mechanical alloyingmethod, the heat treatment is not always necessary. Other methods canalso be used on the condition that they can form the deposit layer.

As a conductive material for the negative electrode, any electronicconductive materials can be used. Examples of such materials includegraphite materials including natural graphite (scale-like graphite)synthetic graphite and expanding graphite; carbon black materials suchas acetylene black, Ketzen black (highly structured furnace black),channel black, furnace black, lamp black and thermal black; conductivefibers such as carbon fibers and metallic fibers; metal powders such ascopper and nickel; and organic conductive materials such aspolyphenylene derivatives. These materials can be used independently orin combination. Among these conductive materials, synthetic graphite,acetylene black and carbon fibers are especially favorable.

The amount of these conductive materials to be added is not specificallydefined, however, 1-50 wt %, especially 1-30% of the negative electrodematerials is desirable. As negative electrode materials (compositeparticles) of the present invention are themselves conductive, even ifconductive materials are not added, the battery can still actuallyfunction. Therefore, the battery has more room available to containcomposite particles.

Binders for the negative electrode can be either thermoplastic resin orthermosetting resin. Desirable binders for the present inventionincludes the following materials; polyethylene, polypropylene,polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),styrene-butadiene rubber, a tetrafluoroethylene-hexafluoropropylenecopolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vinyl ethercopolymer (PFA), a vinyliden fluoride-hexafluoropropylene copolymer, avinyliden fluoride-chlorotrifluoroethylene copolymer, aethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), a vinylidenfluoride-pentafluoropropylene copolymer, a propylene-tetrafluoroethylenecopolymer, a ethylene-chlorotrifluoroethylene copolymer (ECTFE), avinyliden fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, avinyliden fluoride perfluoromethyl vinyl ether-tetrafluoroethylenecopolymer, an ethylene-acrylic acid copolymer or its Na+ ioncrosslinking body, an ethylene-methacrylic acid copolymer or its Na+ ioncrosslinking body, a methyl acrylate copolymer or its Na+ ioncrosslinking body, and an ethylene-methyl methacrylate copolymer or itsNa+ ion crosslinking body. Favorable materials among these materials arestyrene butadiene rubber, polyvinylidene fluoride, an ethylene-acrylicacid copolymer or its Na+ ion crosslinking body, an ethylene-methacrylicacid copolymer or its Na+ ion crosslinking body, a methyl acrylatecopolymer or its Na+ ion crosslinking body, and an ethylene-methylmethacrylate copolymer or its Na+ ion crosslinking body.

As a current collector for the negative electrode, any electronicconductor can be used on the condition that it does not chemicallychange in the battery. For example, stainless steel, nickel, copper,titanium, carbon, conductive resin, as well as copper and stainlesssteel whose surfaces are coated with carbon, nickel or titanium can beused. Especially favorable materials are copper and copper alloys.Surfaces of these materials can be oxidized. It is desirable to treatthe surface of the current collector to make it uneven. Usable forms ofthe foregoing materials as the current collector include a foil, a film,a sheet, a mesh sheet, a punched sheet, a lath form, a porous form, afoamed form and a fibrous form. The thickness is not specificallydefined however, normally those of 1-500 μm in thickness are used.

As positive electrode active materials, lithium compounds or non-lithiumcontaining compounds can be used. Such compounds include Li_(x)CoO₂,Li_(x)NiO₂, Li_(x)MnO₂, Li_(x)Co_(y)Ni_(1−y)O_(z),Li_(x)Co_(y)M_(1−y)O_(z), Li_(x)Ni_(1−y)M_(y)O_(z), Li_(x)Mn₂O₄,Li_(x)Mn_(2−y)M_(y)O₄ (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co,Ni, Cu, Zn, Al, Cr, Pb, Sb and B, and x=0-1, Y=0-0.9, z=2.0-2.3). Thevalue of x is the value before charging and discharging, thus it changesalong with charging and discharging. Other usable positive electrodematerials include transition metal chalcogenides, a vanadium oxide andits lithium compounds, a niobium oxide and its lithium compounds, aconjugate polymer using organic conductive materials, and shevril phasecompounds. It is also possible to use a plurality of different positiveelectrode materials in a combined form. The average diameter ofparticles of the positive electrode active materials is not specificallydefined, however, desirably it is 1-30 μm.

Conductive materials for the positive electrode can be any electronicconductive material on the condition that it does not chemically changewithin the range of charge and discharge electric potentials of thepositive electrode materials in use. Examples of such materials includegraphite materials including natural graphite (scale-like graphite) andsynthetic graphite; carbon black materials such as acetylene black,Ketzen black, channel black, furnace black, lamp black and thermalblack; conductive fibers such as carbon fibers and metallic fibers;fluorinated carbon; metal powders such as aluminum; conductive whiskerssuch as a zinc oxide and potassium titanate, conductive metal oxidessuch as a titanium oxide, and organic conductive materials such aspolyphenylene derivatives. These materials can be used independently orin combination. Among these conductive materials, synthetic graphite andacetylene black are especially favorable.

The total amount of the conductive materials to be added is notspecifically defined, however, 1-50 wt %, especially 1-30% of thepositive electrode materials is desirable. In the case of carbon andgraphite, 2-15 wt % is especially favorable.

Binders for the positive electrode can be either thermoplastic resin orthermosetting resin. The binders for the negative electrode mentionedearlier can be used effectively, however, PVDF and PTFE are morepreferable.

Current collectors for the positive electrode of the present inventioncan be any electronic conductive material on the condition that it doesnot chemically change within the range of charge and discharge electricpotentials of the positive electrode materials in use. For example, thecurrent collectors for the negative electrode mentioned earlier can beused preferably. The thickness of the current collectors is notspecifically defined, however, those of 1-500 μm in thickness are used.

As electrode mixtures for the positive electrode and the negativeelectrode plates, conductive materials, binders, fillers, dispersants,ionic conductors, pressure enhancers, and other additives can be used.Any fiber materials, which do not change chemically in the battery, canbe used as fillers. In general, fibers such as fibers of olefin polymerssuch as polypropylene and polyethylene, and glass fibers and carbonfibers are used as fillers. The amount of the filler to be added is notspecifically defined however, it is desirably 0-30 wt % of the electrodebinders.

As for the construction of the positive electrode and the negativeelectrode, it is favorable that at least the surfaces of the negativeelectrode and the positive electrode where there are the mixtures arefacing each other.

The electrolytic solution is composed of non-aqueous solvent and lithiumsalts dissolved therein.

Examples of non-aqueous solvents include cyclic carbonates such asethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), and vinylene carbonate (VC); acyclic carbonates such as dimethylcarbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC),and dipropyl carbonate (DPC); aliphatic carboxylates such as methylformate, methyl acetate, methyl propionate, and ethyl propionate;gamma-lactones such as gamma-butyrolactone; acyclic ethers such as1,2-dimethoxy ethane (DME), 1,2-diethoxy ethane (DEE), and ethoxymethoxy ethane (EME); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; and non-protonic organic solvents such as dimethylsulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide,dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglime,triester of phosphoric acid, trimethoxy methane, dioxolane derivatives,sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone,3-methyl-2-oxazolidinone, propylene carbonate derivatives,tetrahydrofuran derivatives, ethyl ether, 1,3-propane saltane, anisole,dimethyl sulfoxide and N-methylpyrolidon, These solvents are usedindependently or as a mixture of two or more solvents. Mixtures ofcyclic carbonate and acyclic carbonate, or cyclic carbonate, acycliccarbonate and aliphatic carboxylate are especially favorable.

Lithium salts which dissolve into the foregoing solvents include LiCIO₄,LiBF_(4,), LiPF₆, LiAlCl₄, LiSbF₆, LiSCN, LiCl, LiCF₃SO₃, LiCF₃CO₂, Li(CF₃SO₂)₂, LiAsF₆, LiN(CF₃SO₂)₂, LiB₁₀Cl₁₀, lithium salt of loweraliphatic carboxylic acid, LiCl, LiBr, LiI, chloroboron lithium,4-phenil boric acid, and an imide group. These lithium salts can bedissolved individually or as a mixture of two or more in the non-aqueoussolvents mentioned earlier, and used as an electrolytic solution. It isespecially favorable to include LiPF₆ in the electrolytic solution.

Especially favorable non-aqueous electrolytic solutions of the presentinvention include at least EC and EMC, and as a supporting salt, LiPF₆.The amount of the electrolytic solution to be added to the battery isnot specifically defined. Considering the amount of the positiveelectrode and the negative electrode materials and the size of thebattery, the required amount can be used. The amount of the supportingelectrolytes against the non aqueous solvents is not specificallydefined, however, 0.2-2 mol/l, especially 0.5-1.5 mol/l is preferable.

Instead of an electrolytic solution, the following solid electrolytes,which are categorized into inorganic solid electrolytes and organicsolid electrolytes, can also be used.

Lithium nitrides, lithium halides, and lithium oxides are well knowninorganic solid electrolytes. Among them, Li₄SiO₄, Li₄SiO₄—LiI—LiOH,xLi₃PO₄-(1−x)Li₄SiO₄, Li₂SiS₃, Li₃PO₄—Li₂S—SiS₂ and phosphorus sulfidecompounds are effectively used.

As organic solid electrolytes, polymer materials such as polyethyleneoxides, polypropylene oxides, polyphosphazene, polyaziridine,polyethylene sulfides, polyvinyl alcohol, polyvinylidene fluorides,polyhexafluoropropylene and their derivatives, mixtutres and complexesare effectively used.

It is effective to add other compounds to the electrolytic solution inorder to improve discharge and charge/discharge properties. Suchcompounds include triethyl phosphite, triethanolamine, cyclic ethers,ethylene diamine, n-glime, pyridine, triamide hexaphosphate,nitrobenzene direvatives, crown ethers, quaternary ammonium salt, andethylene glycol dialkyl ether.

As a separator of the present invention, thin films with fine pore,which have a large ion permeability, a predetermined mechanical strengthand insulation properties, are used. It is desirable that the pores ofthe separators close at or above a predetermined temperature to increaseresistance. For the sake of an organic solvent resistance and ahydrophobic property, olefin polymers including polypropylene andpolyethylene can be used individually or in combination. Sheets,non-wovens and wovens made from glass fiber can also be used. Thediameter of the fine pores of the separators is desirably set within therange through which no positive electrode and negative electrodematerials, binding materials, and conductive materials separated fromelectrode sheets can penetrate. A desirable range is, for example,0.01-1 μm. The thickness of the separator is generally 10-300 μm. Theporosity is determined by the permeability of electrons and ions,material and membrane pressure. In general, however, the porosity isdesirably 30-80%.

It is also possible to construct a battery such that polymer materials,which absorb and retain an organic electrolytic solution comprisingsolvents and lithium salts dissolved in the solvents, are included inthe electrode mixtures of the positive and negative electrodes, andporous separators, which comprise polymers capable of absorbing andretaining the organic electrolytic solution, are formed integrally withthe positive and the negative electrode. As the polymer materials, anymaterials capable of absorbing and retaining organic electrolyticsolutions can be adopted. Among such materials, a copolymer ofvinylidene fluoride and hexafluoropropylene is especially favorable.

The following is a detailed description of the materials used in thebatteries of the present invention.

The positive electrode and the negative electrode of the battery of thepresent invention are constructed such that a current collector iscoated with a electrode mixture layer which includes, as mainconstituents, the active materials and the negative electrode materialscapable of electrochemically and reversibly intercalating andde-intercalating lithium ions, and conductive materials as well asbinders.

(Manufacture of the composite particles)

In Table 1, components (pure elements, inter-metallic compound, solidsolution) of the solid phase A and the solid phase B of the compositeparticles used in the preferred embodiments of the present invention,composition ratios of elements, fusion temperatures, and solid phaseline temperatures are shown. Commercially available highly pure reagentsare used as ingredients for each element.

To obtain solid materials, powder or a block of each element containedin the composite particles is put into a fusion vessel in thecomposition ratio shown in Table 1, fused at the fusion temperature alsoshown in Table 1. The fused mixture is quenched by the roll-quenchingmethod and solidified to obtain a solid material which is then heattreated at temperatures of 10° C.-50° C. lower than the solid phase linetemperatures shown in Table 1, in an inert atmosphere for 20 hours.After being heat treated, the material is ground with a ball mill, andclassified using a sieve to prepare composite particles of 45 μm orless. An electron microscope observation confirmed, part of or the wholesurface of composite particles of the solid phase A have covered withthe solid phase B.

FIG. 1 shows a vertical cross section of a cylindrical battery of thepresent invention. In FIG. 1, a positive electrode plate 5 and anegative electrode plate 6 are spirally rolled a plurality of times viaseparators 7, and placed in a battery casing 1. Coming out from thepositive electrode plate 5 is a positive electrode lead 5 a, which isconnected to a sealing plate 2. In the same manner, a negative electrodelead 6 a comes out from a negative electrode plate 6, and is connectedto the bottom of the battery casing 1. Insulating gasket 3 separatessealing plate 2 from battery casing 1.

Electronically conductive metals and alloys having organic electrolyticsolution resistance can be used for the battery casing and lead plates.For example, such metals as iron, nickel, titanium, chromium,molybdenum, copper and aluminum and their alloys can be used. For thebattery casing, stainless steel plate or processed Al-Mn alloy plate isfavorably used, and for the positive electrode lead and the negativeelectrode lead, respectively aluminum and nickel are most favorable. Forthe battery casing, engineering plastics can be used independently orwith metals in order to reduce weight.

Insulating rings 8 are disposed on the top and bottom of an electrodeplate group 4. A safety valve can be used as a sealing plate. Apart fromthe safety valve, other conventionally used safety elements can bedisposed. As an anti-overcurrent element, for example, fuses, bimetaland PTC elements can be used. To deal with increases in internalpressure of the battery casing, a cut can be provided to the batterycasing, a gasket cracking method or a sealing plate cracking method canbe applied, or the connection to the lead plate can be severed. As othermethods, a protective circuit incorporating anti-overcharging andanti-overdischarging systems, can be included in or connectedindependently to a charger. As an anti-overcharging method, current canbe cut off by an increase in internal pressure of the battery. In thiscase, a compound which raises internal pressure can be mixed with theelectrode mixture or with the electrolytes. Such compounds includecarbonates such as Li₂CO₃, LiHCO₃, Na₂CO₃, NaHCO₃, CaCO₃and MgCO₃.

The cap, the battery casing, the sheet and the lead plate can be weldedby conventional methods such as an alternative current or a directcurrent electric welding, a laser welding and an ultrasonic welding. Asa sealing material, conventional compounds and composites such asasphalt can be used.

To prepare the negative electrode plate 6, 20 wt % of carbon powder and5 wt % PVDF are mixed with 75 wt % of the composite particlessynthesized under the foregoing conditions. The mixture is dispersed indehydrated N-methyl pyrrolidone to form a slurry. The slurry is coatedon a negative electrode current collector comprising copper foil, driedand rolled under pressure.

To prepare the positive electrode plate 5, 10 wt % of carbon powder and5 wt % of PVDF are mixed with 85 wt % of lithium cobaltate powder. Themixture is dispersed in dehydrated N-methyl pyrrolidinone to form aslurry. The slurry is coated on a positive electrode current collectorcomprising copper foil, and dried and rolled under pressure.

LiPF6 1.5 mol/l is dissolved in a mixed solvent of EC and EMC which aremixed in a ratio of 1:1 by volume, and used as an electrolytic solution.

Using materials shown in Table 1 for the negative electrode, batteriesare prepared in the manner described above. The cylindrical batteriesprepared are 18 mm in diameter and 65 mm in height.

These batteries are charged at a constant current of 100 mA upto anamounts of 100 atomic percent, 95 atomic percent, 90 atomic percent, 50atomic percent, 30a atomic percent, 20 atomic percent of the theoreticallithium content of the composite particles, and then discharged at theconstant current of 100 mA until their voltage becomes 2.0 V. Thischarge/discharge cycle is repeated in a temperature-controlled oven at20° C. 100 times. The ratio of the discharge capacity at the 100th cycleto that of the initial cycle is defined as the capacity retention rate.The theoretical lithium content capacity ratio of the solid phase A andthe rate of volume expansion of the negative electrode exclusive of thecurrent collector at the 100th cycle are shown in Table 2.

Among the lithium contained in the composite particles, the amountcontained in the solid phase A is calculated based on the analyticalcurve showing the relationship between the amount of lithium anddiffraction peak shift obtained by X ray analysis.

As Table 2 shows, when the solid phase A is Sn, if the lithium contentof the composite particles is 100−50% or that of the solid phase A is100%−40%, the initial discharge capacity is not less than 1600 mAh.However, when the lithium content of the composite particles is 30% orthat of the solid phase A is 20%, the initial discharge capacitydeclines to 1100˜1200 mAh, lower than the battery with conventionalgraphite materials.

As for the discharge capacity at the 100th cycle, when the lithiumcontent of the composite particles is not less than 95% or that of thesolid phase A is not less than 98%, the capacity retention rate becomes91% or less, lowering to the vicinity of 1600 mAh level. Whereas whenthe lithium content of the composite particles is 50-90% or that of thesolid phase A is 40-95%, the capacity retention rate becomes 95% orhigher, maintaining the discharge capacity at the 100th cycle at 1700mAh or more. The volume expansion of the negative electrode exclusive ofthe current collector is 200% or less when the lithium content of thecomposite particle is not more than 90% or that of the solid phase A isnot more than 95%.

When the solid phase A is Si, if the lithium content of the compositeparticles is 100-50%, or that of the solid phase A is 100%−40%, theinitial discharge capacity is not less than 1700 mAh. However, when thelithium content of the composite particles is 30% or that of the solidphase A is 20%, the initial discharge capacity declines to the 1200 mAhlevel, lower than the conventional battery with graphite materials.

As for the discharge capacity at the 100th cycle, when the lithiumcontent of the composite particles is not less than 95% or that of thesolid phase A is not less than 98%, the capacity retention rate becomes91% or less, lowering to the vicinity of 1700 mAh level. Whereas whenthe lithium content of the composite particles is 50-90% or that of thesolid phase A is 40-95%, the capacity retention rate becomes 95% orhigher, maintaining the discharge capacity at the 100th cycle at 1800mAh or more. The volume expansion of the negative electrode exclusive ofthe current collector is 200% or less when the lithium content of thecomposite particle is not more than 90% or that of the solid phase A isnot more than 95%.

When the solid phase A is Zn, if the lithium content of the compositeparticles is 100-50% or that of the solid phase A is 100%−40%, theinitial discharge capacity is not less than 1800 mAh. However, when thelithium content of the composite particles is 30% or that of the solidphase A is 20%, the initial discharge capacity declines to the 1200 mAhlevel, lower than the battery with conventional graphite materials.

As for the discharge capacity at the 100th cycle, when the lithiumcontent of the composite particles is not less than 95% or that of thesolid phase A is not less than 98%, the capacity retention rate becomes91% or less, lowering to the vicinity of 1600˜1700 mAh level. Whereaswhen the lithium content of the composite particles is 50-90% or that ofthe solid phase A is 40-95%, the capacity retention rate becomes 95% orhigher, maintaining the discharge capacity at the 100th cycle at 1800mAh or more. The volume expansion of the negative electrode exclusive ofthe current collector is 200% or less when the lithium content of thecomposite particle is not more than 90% or that of the solid phase A isnot more than 95%.

In all Sn, Si, and Zn cases, it is assumed that the levels of the volumeexpansion of the negative electrode determine the cycle properties.

As thus far described, compared with the conventional batteries usinggraphite as a negative electrode material, the batteries of thisembodiment achieve a higher capacity and superior cycle properties withthe capacity retention rate at the 100th cycle being 95% or higher whenthey satisfy one of the following conditions;

the lithium content of the solid phase A is 40-95 atomic percent of thetheoretical limit of lithium content of each constituent element of thesolid phase A, namely Sn, Si, and Zn;

the lithium content of the solid phase A is 50-90 atomic percent of thetheoretical limit of lithium content of the composite particles; and

the volume expansion rate of the negative electrode exclusive of thecurrent collector is 110-200%.

The second preferred embodiment

The batteries of the first preferred embodiment are charged by thecharging method of the present invention. The charging method of thepresent invention is described in detail below.

FIG. 2 is a graph schematically showing charging current and voltage inaccordance with the charging method of the preferred embodiments of thepresent invention.

In the present invention, the batteries are charged in two chargingregions in combination;

a constant current charging region (CC) applied until the voltage of thebattery reaches a predetermined voltage (V), and in which the batteriesare charged at a constant current level (I); and

a constant voltage charging region (CV) applied after the voltage of thebattery reaches a predetermined voltage (V), and in which the batteriesare charged at a constant voltage of a predetermined voltage level (E).The charging is terminated when the charged current reaches 100 mA inthe constant voltage region.

The charging current (I) represents the density of the electric currentper in the area where the positive and the negative electrodes face eachother. In this embodiments, they are set at 1, 3, 5 and 7 mA/cm². Thepredetermined voltage (V) is 4.1V. The batteries are discharged at theconstant current of 100 mA, discharge is terminated when the voltagereaches 2.0V. The charge/discharge cycle life test is conducted at 20°C.

Comparative Example

A battery is prepared using scale-like synthetic graphite (averageparticle diameter, 25 μm) as a negative electrode material but otherwisein the same manner as the preferred embodiment mentioned earlier. A testis conducted on that battery in the same manner as the preferredembodiments with the exception of setting the current density in thearea where the positive and negative electrodes face each other at 3mA/cm².

Table 3 shows the initial discharge capacity and the discharge capacityof the battery at the 300th cycle as well as the capacity retention ratenamely a ratio of the discharge capacity at the 300th cycle to that ofthe initial cycle.

As Table 3 shows, all of the batteries of the preferred embodiments ofthe present invention enjoy higher initial capacities than the batteryprepared for comparison by using graphite as a negative electrodematerial. When the current density during charging is set at 5 mA/cm² orless, the batteries of the preferred embodiments achieve the capacityretention rate of 70% or higher, showing a better charge/discharge cyclelife property than the comparative battery.

When the batteries are broken at the 300th cycle to visually inspecttheir positive and negative electrodes, separators and electrolyticsolution, the batteries whose capacity retention rates are 70% or lesshave, on the surfaces of the negative electrode and the separators,deposits which are considered to be decomposition products of theelectrolytic solution. The decomposition products inhibit electrodereactions, lowering the discharge capacities. It is considered that thedecomposition products are formed such that when the current densityraises during charging, the negative electrode potential is polarized ina base direction, causing the electrolytic solution to decompose as aside reaction to make deposits.

Thus far described, the charging method for a high-energy densitybattery with superior charge/discharge cycle life properties can beachieved by following the procedure below. The composite particles whosenuclear particles composed of solid phase A are coated with solid phaseB over the whole surface or part of the surface, are used as a negativeelectrode material. The solid phase A contains at least one of tin,silicon and zinc as a constituent element. The solid phase B is composedof a solid solution or an inter-metallic compound composed of at leastone of constituent element of the solid phase A and at least one element(exclusive of the foregoing constituent elements) selected from a groupcomprising group 2 elements, transition elements, group 12 elements,group 13 elements and group 14 elements (exclusive of carbon) of thePeriodic Table. The battery is charged at a predetermined constantcurrent until reaching a predetermined voltage, and subsequently,charged at a predetermined constant voltage. The values of the chargingcurrent in the constant current charging and the constant voltagecharging regions are regulated by setting a current density at the areawhere the positive and the negative electrodes face each other at notmore than 5 mA/cm².

In this embodiment, although the lower limit of the current densityduring charging is set at 1 mA/cm², even lower current density isapplicable. In such a case, however, it takes longer before the batteryis completely charged. Therefore, considering a required chargingduration, the charging current can be set within a range up to 5 mA/cm².It is obvious that, from the view point of the design of the battery,the area of the electrodes can be changed.

Regarding constituent elements of the negative electrode materials, whenthe solid phase A is Sn, Mg selected from group 2 elements, Fe and Mofrom transition elements, Zn and Cd from group 12 elements, In fromgroup 13 elements and Pb from group 14 elements are selected. However,similar results are obtained with other elements selected from eachgroup. The composition ratio of the constituent elements of the negativeelectrode material is not specifically defined, on the condition thattwo phases are created and one of which (solid phase A) is mainlycomposed of Sn, and is partly or entirely covered with the other phase(solid phase B). The solid phase A can be composed not only of Sn butalso traces of other elements such as O, C, N, S, Ca, Mg, Al, Fe, W, V,Ti, Cu, Cr, Co, and P.

When the solid phase A is Si, Mg selected from group 2 elements, Co andNi from transition elements, Zn from group 12 elements, Al from group 13elements and Sn from group 14 elements are used. However, similarresults are obtained with other elements selected from each group.

Similarly, when the solid phase A is Zn, Mg selected from group 2elements, Cu and V from transition elements, Cd from group 12 elements,Al from group 13 elements and Ge from group 14 elements are used.However, similar results are obtained with other elements selected fromeach group. The composition ratio of the constituent elements of thenegative electrode material is not specifically defined, on thecondition that two phases are created and one of which (solid phase A)is mainly composed of Si and Zn, and is partly or entirely covered withthe other phase (solid phase B). The solid phase A can be composed notonly of Si and Zn but also traces of elements such as O, C, N, S, Ca,Mg, Al, Fe, W, V, Ti, Cu, Cr, Co, and P.

The charging method for the batteries of the present invention can beapplied for portable information terminals, portable electronic devices,small size domestic electricity storing devices, motor cycles, electriccars and hybrid electric cars. However, the application of the batteryis not limited to the foregoing.

Applicability in the industry

The batteries and the charging method of the same using the non-aqueouselectrolytes and the composite particles for the negative electrode ofthe present invention help to improve the charge/discharge cycle lifeproperties of high energy-density batteries more than conventionalbatteries using carbon materials as a negative electrode material. Assuch, the batteries of the present invention can be used in portableinformation terminals, portable electronic devices, small size domesticelectricity storing devices, motor cycles, electric cars and hybridelectric cars, thereby offering remarkable benefits when industriallyapplied.

TABLE 1 Negative Melting Solid phase line electrode temperaturetemperature Composition material Phase A Phase B (° C.) (° C.) (Atom %)Material A Sn Mg₂Sn  770 204 Sn:Mg = 50:50 Material B Sn FeSn₂ 1540 513Sn:Fe = 70:30 Material C Sn MoSn₂ 1200 800 Sn:Mo = 70:30 Material D SnZn, Sn Solid S.  420 199 Sn:Zn = 90:10 Material E Sn Cd, Sn Solid S. 232 133 Sn:Cd = 95:5 Material F Sn In, Sn Solid S.  235 224 Sn:In =98:2 Material G Sn Sn, Pb Solid S.  232 183 Sn:Pb = 80:20 Material H SiMg₂Si 1415 946 Si:Mg = 70:30 Material I Si CoSi₂ 1495 1259  Si:Co =85:15 Material J Si NiSi₂ 1415 993 Si:Ni = 69:31 Material K Si Si, ZnSolid S. 1415 420 Si:Zn = 50:50 Material L Si Si, Al Solid S. 1415 577Si:Al = 40:60 Material M Si Si, Sn Solid S. 1415 232 Si:Sn = 50:50Material N Zn Mg₂Zn₁₁  650 364 Zn:Mg = 92.9:7.8 Material O Zn Zn, CuSolid S. 1085 425 Zn:Cu = 97:3 Material P Zn VZn₁₁  700 420 Zn:V = 94:6Material Q Zn Zn, Cd Solid S.  420 266 Zn:Cd = 50:50 Material R Zn Zn,Al Solid S.  661 381 Zn:Al = 90:10 Material S Zn Zn, Ge Solid S.  938394 Zn:Ge = 97:3

TABLE 2 Carging load of Initial 100th capacity Lithium Negative Negativecomposite Discharge Discharge retention content electrode electrodeparticle Capacity Capacity rate of phase A expansion material (%) (mAh)(mAh) (%) (atomic %) (%) 1 Material 100  1872 1685 90 100  260 2 A 951820 1620 89 98 230 3 90 1802 1766 95 95 200 4 50 1755 1702 97 40 110 530 1205 1181 98 20 105 1 B 100  1864 1659 89 100  260 2 95 1870 1664 8998 230 3 90 1849 1757 95 95 200 4 50 1773 1720 97 40 110 5 30 1177 115498 20 105 1 C 100  1847 1625 88 100  260 2 95 1834 1632 98 98 230 3 901825 1734 95 95 200 4 50 1800 1746 97 40 110 5 30 1167 1144 98 20 105 1D 100  1852 1706 90 100  260 2 95 1832 1636 89 98 230 3 90 1829 1737 9595 200 4 50 1778 1725 97 40 110 5 30 1145 1123 98 20 105 1 E 100  18751706 91 100  260 2 95 1874 1668 89 98 230 3 90 1861 1768 95 95 200 4 501813 1759 97 40 110 5 30 1201 1177 98 20 105 1 100  1861 1694 91 100 260 2 95 1852 1649 89 98 230 3 90 1845 1752 95 95 200 4 50 1823 1769 9740 110 5 30 1173 1150 98 20 105 1 G 100  1871 1683 90 100  260 2 95 18481645 89 98 230 3 90 1833 1741 95 95 200 4 50 1774 1721 97 40 110 5 301154 1131 98 20 105 1 H 100  1956 1760 90 100  260 2 95 1931 1718 89 98230 3 90 1967 1869 95 95 200 4 50 1902 1845 97 40 110 5 30 1291 1266 9820 105 1 I 100  1940 1727 89 100  260 2 95 1924 1713 89 98 230 3 90 19111815 95 95 200 4 50 1877 1820 97 40 110 5 30 1259 1234 98 20 105 1 J100  1974 1796 91 100  260 2 95 1973 1755 89 98 230 3 90 1926 1829 95 95200 4 50 1846 1790 97 40 110 5 30 1269 1244 98 20 105 1 K 100  1969 177290 100  260 2 95 1944 1730 89 98 230 3 90 1918 1822 95 95 200 4 50 18781821 97 40 110 5 30 1269 1244 98 20 105 1 L 100  1989 1750 88 100  260 295 1966 1749 89 98 230 3 90 1921 1824 95 95 200 4 50 1869 1812 97 40 1105 30 1266 1241 98 20 105 1 M 100  1981 1783 90 100  260 2 95 1949 173489 98 230 3 90 1902 1806 95 95 200 4 50 1882 1825 97 40 110 5 30 12451221 98 20 105 1 N 100  1939 1764 91 100  260 2 95 1920 1708 89 98 230 390 1905 1809 95 95 200 4 50 1874 1717 97 40 110 5 30 1264 1239 98 20 1051 O 100  1945 1751 90 100  260 2 95 1922 1710 89 98 230 3 90 1911 181595 95 200 4 50 1885 1828 97 40 110 5 30 1234 1211 98 20 105 1 P 100 1901 1692 89 100  260 2 95 1882 1674 89 98 230 3 90 1878 1802 96 95 2004 50 1860 1805 97 40 110 5 30 1226 1202 98 20 105 1 Q 100  1910 1719 90100  260 2 95 1901 1708 89 98 230 3 90 1894 1800 95 95 200 4 50 18581803 97 40 110 5 30 1223 1199 98 20 105 1 R 100  1949 1754 90 100  260 295 1922 1749 89 98 230 3 90 1894 1800 95 95 200 4 50 1860 1805 97 40 1105 30 1216 1192 98 20 105 1 S 100  1909 1697 89 100  260 2 95 1897 168989 98 230 3 90 1885 1809 95 95 200 4 50 1856 1801 97 40 110 5 30 12221198 98 20 105 Graphite — 1510 1389 92 110

TABLE 3 Initial 100th Negative Current Discharge Discharge capacityelectrode density Capacity Capacity retention rate material (mA/cm²)(mAh) (mAh) (%)  1 Material 1 1870 1495 78  2 A 3 1868 1401 75  3 5 18601302 70  4 7 1859 1153 62  5 B 1 1864 1491 80  6 3 1862 1490 80  7 51859 1394 75  8 7 1855 1168 63  9 C 1 1847 1422 77 10 3 1842 1400 76 115 1838 1342 73 12 7 1830 1116 61 13 D 1 1852 1482 80 14 3 1849 1442 7815 5 1846 1403 76 16 7 1841 1178 64 17 E 1 1876 1520 81 18 3 1873 149880 19 5 1869 1458 78 20 7 1862 1210 65 21 F 1 1863 1453 78 22 3 18611377 74 23 5 1861 1302 70 24 7 1859 1153 62 25 G 1 1871 1553 83 26 31868 1494 80 27 5 1866 1418 76 28 7 1864 1212 65 29 H 1 1956 1584 81 303 1955 1525 78 31 5 1951 1483 76 32 7 1948 1227 63 33 I 1 1940 1582 8034 3 1938 1550 80 35 5 1936 1491 77 36 7 1930 1177 61 37 J 1 1974 155979 38 3 1973 1539 78 39 5 1971 1518 77 40 7 1969 1260 64 41 K 1 1969 15679 42 3 1965 1493 76 43 5 1965 1454 74 44 7 1960 1176 60 45 L 1 19891651 83 46 3 1983 1606 81 47 5 1983 1547 78 48 7 1976 1284 65 49 M 11981 1624 82 50 3 1981 1605 81 51 5 1976 1462 74 52 7 1973 1223 62 53 N1 1939 1532 79 54 3 1935 1471 76 55 5 1933 1411 73 56 7 1929 1138 59 57O 1 1945 1537 79 58 3 1945 1498 77 59 5 1940 1416 73 60 7 1935 1180 6161 P 1 1901 1445 76 62 3 1898 1386 73 63 5 1895 1345 71 64 7 1890 109658 65 Q 1 1920 1536 80 66 3 1918 1496 78 67 5 1915 1417 74 68 7 19091241 65 69 R 1 1949 1579 81 70 3 1948 1539 79 71 5 1946 1421 73 72 71941 1165 60 73 S 1 1907 1468 77 74 3 1903 1408 74 75 5 1901 1350 71 767 1899 1082 57

What is claimed is:
 1. A non-aqueous electrolyte secondary batterycomprising: a positive electrode, a negative electrode capable ofintercalating and de-intercalating lithium, a non-aqueous electrolytesolution, and a separator or a solid electrolyte, wherein: said negativeelectrode comprises a plurality of composite particles, each of saidcomposite particles comprises a central portion comprising lithium andat least one element selected from the group consisting of tin, siliconand zinc; and a coating at least partially around said central portion,said coating comprising solid solution or an inter-metallic compound,said solid solution or inter-metallic compound comprising a) said atleast one element selected from the group consisting of tin, silicon andzinc, and b) at least one element selected from the group consisting ofgroup 2 elements, transition elements, group 12 elements, group 13elements and group 14 elements exclusive of carbon, and exclusive ofsaid at least element selected from the group consisting of tin,silicon, and zinc; wherein the lithium content of said central portionis 40-95 atomic percent of the theoretical lithium content limit of thecentral portion.
 2. The non-aqueous electrolyte secondary battery ofclaim 1, wherein the lithium content of said central portion is 50-90atomic percent of the theoretical lithium content limit of the centralportion.
 3. A non-aqueous electrolyte secondary battery comprising: apositive electrode, a negative electrode capable of intercalating andde-intercalating lithium, said negative electrode comprising a currentcollector, a non-aqueous electrolyte solution, and a separator or asolid electrolyte, wherein: said negative electrode comprises aplurality of composite particles, each of said composite particlescomprises a central portion comprising lithium and at least one elementselected from the group consisting of tin, silicon and zinc; and acoating at least partially around said central portion, said coatingcomprising a solid solution or an inter-metallic compound; said solidsolution or inter-metallic compound comprising a) said at least oneelement selected from the group consisting of tin, silicon and zinc, andb) at least one element selected from the group consisting of group 2elements, transition elements, group 12 elements, group 13 elements andgroup 14 elements exclusive of carbon, and exclusive of said at leastelement selected from the group consisting of tin, silicon, and zinc;wherein the volume expansion of said negative electrode exclusive of thecurrent collector is 110-200% when said negative electrode contains anamount of lithium which prevents deposit of lithium on said negativeelectrode.
 4. A method charging of a non-aqueous electrolyte secondarybattery, said method comprising the steps of: providing said battery,said battery comprising a positive electrode and a negative electrode;wherein the negative electrode comprises a plurality of compositeparticles each of said composite particle comprises a central portioncomprising lithium and at least one element selected from the groupconsisting of tin, silicon and zinc; and a coating at least partiallyaround said central portion, said coating comprising a solid solution oran inter-metallic compound, said solid solution or inter-metalliccompound a) said at least one element selected from the group consistingof tin, silicon and zinc, and b) at least one element selected from thegroup consisting of group 2 elements, transition elements, group 12elements, group 13 elements and group 14 elements exclusive of carbon,and exclusive of said at least element selected from the groupconsisting of tin, silicon, and zinc; charging said battery at aconstant current until reaching a predetermined voltage, and chargingsaid battery at said predetermined voltage after reaching saidpredetermined voltage, said predetermined voltage producing a current;wherein said constant current and said current produced by saidpredetermined voltage are at not more than 5 mA/cm2 current density atan area where said positive electrode and said negative electrodes faceeach other.
 5. A non-aqueous electrolyte secondary battery comprising; apositive electrode, a negative electrode capable of intercalating andde-intercalating lithium, a non-aqueous electrolyte solution, and eithera separator or a solid electrolyte; wherein: the negative electrodecomprises a plurality of composite particles; each of said compositeparticles comprise a nuclear particle consisting essentially of lithiumand an element selected from the group consisting of tin, silicon, andzinc; at least a part of a surface of each of the nuclear particles iscoated with either a solid solution or an inter-metallic compound; saidsolid solution or intermetallic compound comprises said element selectedfrom the group consisting of tin, silicon, and zinc and at least oneadditional element; said additional is selected from the groupconsisting of group 2 elements, transition elements, group 12 elements,group 13 elements, and group 14 elements exclusive of carbon, andexclusive of said element selected from the group consisting of tin,silicon, and zinc, and the lithium content of said central portion is40-95 atomic percent of the theoretical lithium content limit of thecentral portion.
 6. The non-aqueous electrolyte secondary battery ofclaim 5, wherein the element selected from the group consisting of tin,silicon, and zinc is tin.
 7. The non-aqueous electrolyte secondarybattery of claim 5, wherein the element selected from the groupconsisting of tin, silicon, and zinc is silicon.
 8. The non-aqueouselectrolyte secondary battery of claim 5, wherein the element selectedfrom the group consisting of tin, silicon, and zinc is zinc.
 9. Thenon-aqueous electrolyte secondary battery of claim 5, wherein theadditional element is selected from the group consisting of Mg, Fe, Mo,Zn, Cd, In, Pb, Co, Ni, Al, Sn, Cu, V, and Ge.
 10. The non-aqueouselectrolyte secondary battery of claim 5, wherein the lithium content ofsaid central portion is 50-90 atomic percent of the theoretical lithiumcontent limit of the central portion.
 11. The non-aqueous electrolytesecondary battery of claim 3, wherein the element selected from thegroup consisting of tin, silicon, and zinc is tin.
 12. The non-aqueouselectrolyte secondary battery of claim 3, wherein the element selectedfrom the group consisting of tin, silicon, and zinc is silicon.
 13. Thenon-aqueous electrolyte secondary battery of claim 3, wherein theelement selected from the group consisting of tin, silicon, and zinc iszinc.
 14. The method of claim 4, wherein the element selected from thegroup consisting of tin, silicon, and zinc is tin.
 15. The method ofclaim 4, wherein the element selected from the group consisting of tin,silicon, and zinc is silicon.
 16. The method of claim 4, wherein theelement selected from the group consisting of tin, silicon, and zinc iszinc.
 17. A method charging of a non-aqueous electrolyte secondarybattery, said method comprising the steps of: providing said battery,said battery comprising a positive electrode and a negative electrode;wherein the negative electrode comprises a plurality of compositeparticles each of said composite particle comprises a central portionconsisting essentially of lithium and at least one element selected fromthe group consisting of tin, silicon and zinc; and a coating at leastpartially around said central portion, said coating comprising a solidsolution or an inter-metallic compound, said solid solution orinter-metallic compound a) said at least one element selected from thegroup consisting of tin, silicon and zinc, and b) at least one elementselected from the group consisting of group 2 elements, transitionelements, group 12 elements, group 13 elements and group 14 elementsexclusive of carbon, and exclusive of said at least element selectedfrom the group consisting of tin, silicon, and zinc; charging saidbattery at a constant current until reaching a predetermined voltage,and charging said battery at said predetermined voltage after reachingsaid predetermined voltage said predetermined voltage producing acurrent; wherein said constant current and said current produced by saidpredetermined voltage are at not more than 5 mA/cm2 current density atan area where said positive electrode and said negative electrodes faceeach other.
 18. The method of claim 17, wherein the element selectedfrom the group consisting of tin, silicon, and zinc is tin.
 19. Themethod of claim 17, wherein the element selected from the groupconsisting of tin, silicon, and zinc is silicon.
 20. The method of claim17, wherein the element selected from the group consisting of tin,silicon, and zinc is zinc.